Development of an easy aqueous sol-gel synthesis for large-scale film deposition methods for the manufacture of coated steel with self-cleaning properties

In this work, a global process has been developed to produce at a large scale pure TiO2 films deposited on steel in order to get an easy-to-clean surface. This large scale process implies an easy aqueous sol-gel process for the synthesis of the TiO2 sol. This synthesis [1] has been simplified to make easier the extrapolation towards an industrial scale. Results of TEM, photocatalytic properties, film hydrophilicity, and texture obtained with the simplified aqueous sol-gel synthesis (IsoP-TiO2 synthesis) show similar properties than those obtained with the standard aqueous sol-gel synthesis of TiO2 developed previously (HAc-TiO2 synthesis [2]). Only XRD patterns were slightly different with the presence of anatase-brookite phases in IsoP-TiO2 synthesis while anatase phase only was observed in HAc-TiO2 synthesis. Both the aqueous sol-gel synthesis of pure TiO2 and the film deposition on steel by roll-coating have been successfully extrapolated to a larger scale. Indeed, the deposition was done on a pilot line, the steel substrate is 25 cm width, and the band length is 800 m. The coating was deposited at line speed ranging from 30 to 120 m.min-1.The photocatalytic activity and the hydrophilicity of the film were found to be unchanged compared to the films produced at a laboratory scale, thus validating the production of an efficient easy-to-clean material. Even if some problems have still to be solved, this study is a hopeful first step in the development of a large scale process for self-cleaning steel production.
[1] S. Mahshid, M. Askari, M.S. Ghamsari, J. Mater. Process. Technol. 189 (2007) 296–300
[2] C.M. Malengreaux, S. Douven, D. Poelman, B. Heinrichs, J.R. Bartlett, J. Sol-Gel Sci. Technol. 71 (2014) 557–570